This invention relates to conveyor belt scraper blades, and more particularly, to blades for scraping and cleaning of high speed conveyor belts.
Cleaning the return side of a high speed conveyor belt that carries loose bulk materials has always been a particularly difficult challenge for industrial and mining companies. While various designs have achieved successes in many areas, the companies operating high speed conveyors are constantly demanding continued improvements in performance from belt cleaning equipment. There are two areas that are of primary concern for scraper blade design: the first is cleaning performance; the second is scraper blade life.
Prior designs for scraper blades have incorporated various materials for the scraper blade media, including rubber urethane, steel and tungsten carbide.
The product offerings in metal blade media by other companies have, for the most part, been of a segmented design where a cleaner blade with a metal tip is designed with a plurality of individual elements, typically 2xe2x80x3 to 6xe2x80x3 in width thus requiring eight to twenty-four elements to clean a conveyor belt of 48xe2x80x3 width. These elements are typically of cast urethane design with a small piece of tungsten carbide typically {fraction (3/16)}xe2x80x3 thickxc3x97xc2xdxe2x80x3 high, molded to the wear edge of the cleaning element. The segmented design offers advantages and disadvantages. The elements are typically light weight and easy to handle. The fact that multiple units are used to cover the width of a conveyor belt however means that there is a joint between each element that can allow carryback material to pass between elements if the elements are not perfectly aligned and positioned.
Typical prior art metal edge cleaner blades of segmented design are installed with the tungsten edge at an aggressive attack angle to the conveyor belt. The accepted angle is typically 10 to 30 degrees beyond perpendicular to the conveyor belt. This design places the tungsten tip of the blade in sole contact with the conveyor belt. The hard urethane substrate portion of the element is used only as a tensioning device and as a device for possible pressure relief if the element is over stressed. There is no other support or protection for the conveyor belt. The conveyor belt is arched across the exposed tungsten cleaner blade edge. The design of the typical tension system is such that when irregular portions of the conveyor belt pass, the pressure applied by the conveyor belt toward the scraper blade is increased and the resistance of the scraper blade to the belt is increased as the flexing motion is limited by the elasticity of the urethane polymer being used to hold the tungsten carbide blade tip.
This aggressive attack angle for prior art blades and the fact that the tungsten tip is the sole portion of the element in contact with the conveyor belt means that any irregularities in the conveyor belt including vulcanized splices, metal splices and hanging threads are subject to serious damage from the tungsten cleaner edge.
The design of the cast urethane segments or elements with tungsten carbide tip is typically of a shape and configuration that allows each element to flex in the direction of belt travel. The hard urethane base that holds the tungsten tip is typically a hard material in the range of 85 to 90 durometer shore A hardness. This hard material does not move behind the tungsten tip and any flexing of the urethane element is accomplished by the structural design of the element. For example, the element is molded with a hollow cavity in it to make the support thinner and thereby allow it to bend. This is supposed to help prevent damage being caused to the conveyor belt by the element if a metal splice or some irregularity in the conveyor belt should pass the cleaner blade.
Accordingly, there is a continuing need for a scraper blade structure which effectively cleans high speed conveyors and which has an extended useful life and, in particular, there is a need for a continuous non-segmented blade using tungsten carbide or similar rigid media such as steel.
The present invention provides a scraper blade assembly which is configured to provide a rigid material scraping edge supported on a resiliently compliant material such that the scraping edge is adapted to move in response to irregularities in an associated conveyor belt. Further, supporting structure for the resiliently compliant material is configured so as to promote an upward deformation of the resiliently compliant material when a compressive force is applied to the rigid material scraping edge to thereby form the resiliently compliant material as a supporting surface above the scraping edge when such a force is applied.
In accordance with one aspect of the invention, a scraper blade assembly for a conveyor belt scraper is provided comprising: an elongated blade body including a resilient backing member formed of a resilient material and defining a central longitudinal scraper blade axis, the resilient backing member including opposing sides, first and second faces extending longitudinally between the sides, and an upper surface located between the first and second faces and extending longitudinally between the sides; a longitudinally extending support frame attached to the elongated body and defining opposing first and second ends; end plates attached to the first and second ends for attaching the blade assembly to support structure such that the elongated body extends transversely of an associated conveyor belt; and the elongated body further including an elongated metal face plate attached to the first face of the resilient backing member and comprising a continuous strip of material having an upper edge adjacent the upper surface extending from the first end to the second end of the support frame.
In accordance with another aspect of the invention, a scraper blade assembly for a conveyor belt scraper is provided comprising: an elongated blade body including a resilient backing member formed of a resilient material and defining a central longitudinal scraper blade axis, the resilient backing member including opposing sides, first and second faces extending longitudinally between the sides, and an upper surface located between the first and second faces and extending longitudinally between the sides; a longitudinally extending support frame attached to the elongated body for supporting the elongated body extending transversely of an associated conveyor belt; the resilient backing member including an upper portion extending upwardly from an upper edge of the support frame; the elongated body further including an elongated metal face plate attached to the first face of the resilient backing member at the upper portion and having an upper edge adjacent the upper surface of the resilient backing member; a rigid backing member extending upwardly from the upper edge of the support frame along a substantial portion of the second face of the resilient backing member for supporting the upper portion of the resilient backing member against movement when a force is applied against the metal face plate.
In accordance with yet another aspect of the invention, a scraper blade assembly for a conveyor belt scraper is provided comprising: an elongated blade body including a resilient backing member formed of a resilient material and defining a central longitudinal scraper blade axis, the resilient backing member including opposing sides, first and second faces extending longitudinally between the sides, and an upper surface located between the first and second faces and extending longitudinally between the sides; a longitudinally extending support frame attached to the elongated body for supporting the elongated body extending transversely of an associated conveyor belt; the resilient backing member including an upper portion extending upwardly from an upper edge of the support frame; the elongated body further including an elongated rigid face plate attached to the first face of the resilient backing member at the upper portion and having an upper edge for scraping material from an associate conveyor belt, the upper surface of the resilient backing member being coextensive with the upper edge of the face plate for providing support to the conveyor belt; the rigid face plate comprising a continuous rigid structure supported out of contact with the support structure, and extending the entire length of the elongated blade body for extending substantially the entire width of an associated conveyor belt; a rigid backing member extending upwardly from the upper edge of the support frame along a substantial portion of the second face of the resilient backing member for supporting the upper portion of the resilient backing member against movement when a force is applied against the rigid face plate.
Other aspects of the invention will be apparent from the following description, the accompanying drawings and the appended claims.